{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-75588", "assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "state": "PUBLISHED", "assignerShortName": "Mattermost", "dateReserved": "2026-08-17T22:19:32.227Z", "datePublished": "2026-09-17T15:09:40.829Z", "dateUpdated": "2026-09-17T15:09:40.829Z"}, "containers": {"cna": {"affected": [{"defaultStatus": "unaffected", "product": "Mattermost", "vendor": "Mattermost", "versions": [{"lessThanOrEqual": "6.2.2", "status": "affected", "version": "0", "versionType": "semver"}, {"version": "6.3.0", "status": "unaffected"}, {"version": "6.2.3.0", "status": "unaffected"}]}], "credits": [{"lang": "en", "type": "finder", "value": "Juho Fors\u00e9n"}], "descriptions": [{"lang": "en", "value": "Mattermost Desktop App versions <=6.2 6.2.2.0 fail to validate the URL scheme when checking whether a target URL is internal to the connected server, which allows a network-positioned attacker to load a plugin popout window over an insecure connection via a link using a downgraded URL scheme. Mattermost Advisory ID: MMSA-2026-00717"}], "metrics": [{"cvssV3_1": {"attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "NONE", "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:L/A:N", "baseSeverity": "LOW", "baseScore": 2.6}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "description": "CWE-1287: Improper Validation of Specified Type of Input", "cweId": "CWE-1287"}]}], "references": [{"url": "https://mattermost.com/security-updates", "name": "MMSA-2026-00717", "tags": ["vendor-advisory"]}], "solutions": [{"value": "Update Mattermost Desktop App to versions 6.3.0, 6.2.3.0 or higher.", "lang": "en"}], "source": {"advisory": "MMSA-2026-00717", "defect": ["https://mattermost.atlassian.net/browse/MM-69786"], "discovery": "{\"self\"=>\"https://mattermost.atlassian.net/rest/api/2/customFieldOption/10557\", \"value\"=>\"Internal\", \"id\"=>\"10557\"}"}, "title": "Mattermost Desktop App plugin popout scheme validation bypass", "providerMetadata": {"orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "shortName": "Mattermost", "dateUpdated": "2026-09-17T15:09:40.829Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}}}

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Mattermost", "vendor": "Mattermost", "versions": [{"lessThanOrEqual": "6.2.2", "status": "affected", "version": "0", "versionType": "semver"}, {"status": "unaffected", "version": "6.3.0"}, {"status": "unaffected", "version": "6.2.3.0"}]}], "source": "responsibledisclosure@mattermost.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Mattermost Desktop App versions <=6.2 6.2.2.0 fail to validate the URL scheme when checking whether a target URL is internal to the connected server, which allows a network-positioned attacker to load a plugin popout window over an insecure connection via a link using a downgraded URL scheme. Mattermost Advisory ID: MMSA-2026-00717"}], "id": "CVE-2026-75588", "lastModified": "2026-09-17T16:17:41.940", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 2.6, "baseSeverity": "LOW", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 1.2, "impactScore": 1.4, "source": "responsibledisclosure@mattermost.com", "type": "Secondary"}]}, "published": "2026-09-17T16:17:41.940", "references": [{"source": "responsibledisclosure@mattermost.com", "url": "https://mattermost.com/security-updates"}], "sourceIdentifier": "responsibledisclosure@mattermost.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-1287"}], "source": "responsibledisclosure@mattermost.com", "type": "Secondary"}]}

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{}